On 1969-1976 Corvettes, there are many items in the interior that need attention. By now, most of these cars have replacement interiors, but one of the items that is often overlooked is the air conditioning/heater control panel. Although it appears to be a very complicated piece for the average hobbyist to rebuild, with our step-by-step procedures it should be, as they say in Jamaica, “No Problem, Mon.” Just follow along and we’ll show you how to rebuild your control unit with a kit from Zip Corvette Parts.
You will also learn how to “set” the switches and, for those of you with a unit that doesn’t work at all, this will be a great fix. Not only will your unit function, it will also look great inside your Corvette’s interior. You can expect a couple of hours to complete this procedure, including removing the unit from your Corvette’s console, which also requires removing the shift plate and the vacuum lines and cables from the heater/air condition unit. This rebuild will also work for 1968 Corvettes, except they do not have any vacuum lines attached to the heater control unit.
Click on the images for expanded views – it’s much easier on the eyes.
01: As you can see, our Corvette’s heater control unit was in very bad shape. It’s hard to believe we will be able to make it look new again.
02: To get started, remove the large cover and switch assembly on the left side. Be sure to put the 1/4-inch screws in a place where you will not lose them.
03: You can reuse these switches if they are good. Check them by depressing the black plastic slide to see if the contact opens. If the contact does not open, you will need to replace the switch. We had to replace both of the compressor and low blower switch.
04: With both switches off, remove the vacuum switch on the left side. Some years, depending on options, will also have a 3-outlet vacuum switch on the right side. Remove them both if your Corvette has them. Once those are off, remove the blower switch in the middle of the control unit. The support bar in front that attaches both sides also needs to be removed. Then remove the four 1/4-inch screws that hold the sides to the face, then discard the old face.
05: Remove the plastic thumb wheels by using a set of pliers or dykes to cut off the retaining clip, then the wheels will slide out and you can discard them.
06: These are parts you need to keep. Now is a good time to clean off 20-30 of residue.
07: Zip Corvette Parts supplied all the components needed to rebuild our Corvette’s heater/air conditioned control panel.
08: With the parts clean, start reassembling. We started by applying lithium grease to the control shafts before installing them.
09: With the control shafts greased, bolt them to the heater/AC +control unit halves. There is a left and a right on A/C cars; the shaft with the flat side will go on the left half.
10: You will need to calibrate each half to the control face. First, install one of the plastic wheels into one of the halves. Roll the wheel forward until it stops and note the position of the shaft. It should be all the way back, which is the location of the shaft when the control unit is in the off position.
11: Now, remove the thumb wheel from the control half you just set and install it in the control face. Once the wheel is locked in the control face, roll the wheel all the way forward to the off position.
12: With the control face in the off position, install the correct side half. Leave the wheel in the control face while you slide the side onto the gear side of the plastic wheel. Once the side is seated, you can bolt it in place. Repeat this step for the opposite side.
13: After both sides are bolted on, install the front cross brace, then the low blower switch. Go ahead and place the switch in its location, but do not tighten the screw. Roll the left wheel down until you get to bi-level. This is where you need to adjust the switch so the contact is open when the indicator is in this position. Once it is set, tighten the screw to lock it in place.
14: Now screw the vacuum switch in place. Again, some Corvettes with certain options will have vacuum ports on both sides of the heater/AC control panel.
15: Install the compressor switch assembly, leaving the indicator in the bi-level position and bolting the switch in place. Now roll the wheel forward to the off position. The contact should open when the indictor gets to the off position, If not, then readjust.
16: Now check your Corvette’s heater/AC control unit and make sure that both switches are operating correctly. If they are, then you can install the clips that press over the end of the control wheel. Use a large socket to press the clip on. Now you’re ready to install your new heater control unit back in your C3 Corvette.
1968-1976 Heat/AC Control Panel Rebuild
Text and images by Justin Abbott
Source: Zip Corvette Parts
8067 Fast Lane | Mechanicsville, VA 23111 | (800) 962-9632
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